Microsoft Windows Kernel Information Disclosure
CVE-2021-31955 is a medium-severity exposure of sensitive system information to an unauthorized control sphere vulnerability in Windows 10 Version 1809 from Microsoft, with a CVSS 3.1 base score of 5.5 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists version 10.0.17763.1999 as the first without the flaw, so updating Windows 10 Version 1809 to that release or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on November 3, 2021, which means attacks have been observed in the wild.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update Windows 10 Version 1809 to 10.0.17763.1999 or a later version.
- Update Windows Server 2019 to 10.0.17763.1999 or a later version.
- Update Windows Server 2019 (Server Core installation) to 10.0.17763.1999 or a later version.
- CISA's required action: Apply updates per vendor instructions.
- Read the advisory on portal.msrc.microsoft.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Microsoft | Windows 10 Version 1809 | 10.0.0 up to, but not including, 10.0.17763.1999 | 10.0.17763.1999 |
| Microsoft | Windows Server 2019 | 10.0.0 up to, but not including, 10.0.17763.1999 | 10.0.17763.1999 |
| Microsoft | Windows Server 2019 (Server Core installation) | 10.0.0 up to, but not including, 10.0.17763.1999 | 10.0.17763.1999 |
| Microsoft | Windows 10 Version 1909 | 10.0.0 up to, but not including, 10.0.18363.1621 | 10.0.18363.1621 |
| Microsoft | Windows 10 Version 21H1 | 10.0.0 up to, but not including, 10.0.19043.1052 | 10.0.19043.1052 |
| Microsoft | Windows 10 Version 2004 | 10.0.0 up to, but not including, 10.0.19041.1052 | 10.0.19041.1052 |
| Microsoft | Windows Server version 2004 | 10.0.0 up to, but not including, 10.0.19041.1052 | 10.0.19041.1052 |
| Microsoft | Windows 10 Version 20H2 | 10.0.0 up to, but not including, 10.0.19042.1052 | 10.0.19042.1052 |
| Microsoft | Windows Server version 20H2 | 10.0.0 up to, but not including, 10.0.19042.1052 | 10.0.19042.1052 |
| Microsoft | Windows 10 1809 | before 10.0.17763.1999 | 10.0.17763.1999 |
| Microsoft | Windows 10 1909 | before 10.0.18363.1621 | 10.0.18363.1621 |
| Microsoft | Windows 10 2004 | before 10.0.19041.1052 | 10.0.19041.1052 |
| Microsoft | Windows 10 20h2 | before 10.0.19042.1052 | 10.0.19042.1052 |
| Microsoft | Windows 10 21h1 | before 10.0.19043.1052 | 10.0.19043.1052 |
| Microsoft | Windows Server 2004 | before 10.0.19041.1052 | 10.0.19041.1052 |
| Microsoft | Windows Server 20h2 | before 10.0.19042.1052 | 10.0.19042.1052 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- NoneNothing can be modified.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 5.5 | Medium | CNA (microsoft.com) |
| CVSS 3.1 | 5.5 | Medium | NVD |
| CVSS 2.0 | 2.1 | Low | NVD |
Official description
Windows Kernel Information Disclosure Vulnerability
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Exposure of Sensitive System Information to an Unauthorized Control Sphere
The product does not properly prevent sensitive system-level information from being accessed by unauthorized actors who do not have the same level of access to the underlying system as the product does.
How developers prevent this class of flaw
- Production applications should never use methods that generate internal details such as stack traces and error messages unless that information is directly committed to a log that is not viewable by the end user. All error message text should be HTML entity encoded before being written to the log file to protect against potential cross-site scripting attacks against the viewer of the logs
Timeline
- CVE record published.
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Third-party and government advisories
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-31955US Government Resource
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